Molded case circuit breaker actuator-accessory module

ABSTRACT

An integrated protection unit is a circuit breaker which includes basic overcurrent protection facility along with selective electrical accessories. A molded plastic accessory access cover secured to the integrated protection unti cover protects the accessory components contained within the integrated protection unit cover from the environment. A combined overcurrent trip actuator and multiple accessory module is either field-installed or factory-installed within the integrated protection unit. A separate actuator-accessory module is selected for different combinations of accessory functions.

BACKGROUND OF THE INVENTION

The trend in the circuit protection industry is currently towardcomplete circuit protection which is accomplished by the addition ofsupplemental protection apparatus to standard overcurrent protectivedevices, such as molded case circuit breakers. U.S. Pat. 4,622,444entitled "Circuit Breaker Housing and Attachment Box" describes anaccessory that can be field-installed within a circuit breaker withoutinterfering with the integrity of the circuit breaker internalcomponents. This is accomplished by mounting the accessories within arecess formed in the circuit breaker enclosure cover.

An electronic trip actuator which is mounted within the circuit breakerenclosure is described within U.S. Pat. No. 4,679,019 entitled "TripActuator for Molded Case Circuit Breakers". The circuit breaker actuatorresponds to trip signals generated by an electronic trip unit completelycontained within a semi-conductor chip such as that described withinU.S. Pat. No. 4,589,052. The development of a combined trip actuator forboth overcurrent protection as well as accessory function is foundwithin U.S. Pat. No. 4,700,161 entitled Trip Unit and Accessory Modulefor Electronic Trip Circuit Breakers". The aforementioned U.S. Patentswhich represent the advanced state of the art of circuit protectiondevices are incorporated herein for reference purposes.

A shunt trip accessory unit allows the circuit breaker operatingmechanism to be articulated to separate the circuit breaker contacts,usually to perform a tripping function for electrical system control andprotection. One such shunt trip accessory unit is described within U.S.patent application Ser. No. 133,867 filed Dec. 16, 1987 entitled "MoldedCase Circuit Breaker Shunt Trip Unit". An auxiliary switch accessoryunit allows an operator to determine the "ON" or "OFF" conditions of amolded case circuit breaker contacts at a remote location by means of anaudible alarm or visible display. One such auxiliary switch unit isdescribed within U.S. patent application Ser. No. 133,868 filed Dec. 16,1987 entitled "Molded Case Circuit Breaker Auxiliary Switch Unit". Bothof the aforementioned U.S. Patent Applications are incorporated hereinfor purposes of reference.

One example of an undervoltage release circuit is found within UnitedKingdom patent application 2,033,177A entitled "Circuit Breaker withUndervoltage Release". The circuit described within this Applicationapplies a large initial current pulse to the undervoltage release coilto drive the plunger against the bias of a powerful compression springand uses a ballast resistor to limit the holding current to theundervoltage release coil to a lower value. It is believed that the heatgenerated within this circuit would not allow the circuit to becontained within the confines of the circuit breaker enclosure.

A more recent example of a combined overcurrent trip actuator andmultiple accessory unit is described within U.S. patent application Ser.No. 133,869 filed Dec. 16, 1987 entitled "Molded Case Circuit BreakerMultiple Accessory Unit" which combined overcurrent trip actuator andmultiple accessory unit requires a separate mounting recess within thecircuit breaker cover to house the printed wire board that carries theaccessory control circuit. U.S. patent application Ser. No. 163,589entitled "Molded Case Circuit Breaker Actuator-Accessory Unit" describesone such combined overcurrent trip actuator and multiple accessory unitwherein the printed wire board and actuator-accessory unit are bothcontained within the same mounting recess within the circuit breakercover. Both of the aforementioned U.S. patent applications areincorporated herein for purposes of reference.

SUMMARY OF THE INVENTION

An integrated protection unit which includes overcurrent protectionalong with auxiliary accessory function within a common enclosurecontains an accessory cover for access to the selected accessory modulesto allow field installation of the accessory modules. A combinedactuator-accessory module provides overcurrent along with undervoltagerelease and/or shunt trip functions and is arranged along with theprinted wire board containing the accessory control circuit within onepart of the enclosure. A separate module is required for overcurrentwith undervoltage protection; overcurrent with shunt trip; andovercurrent with both shunt trip along with undervoltage protection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top perspective view of an integrated molded case circuitbreaker containing selected accessory functions;

FIG. 2 is an exploded top perspective view of the integrated circuitbreaker of FIG. 1 prior to assembly of the combined actuator-accessorymodule according to the invention;

FIG. 3 is a plan view of the integrated molded case circuit breaker withpart of the cover removed to show the interaction between the circuitbreaker operating mechanism and the combined actuator-accessory module;

FIG. 4 is a circuit diagram of one embodiment of the electrical circuitcontained within the printed wire board on the actuator-accessory moduleof FIG. 2;

FIG. 5 is a circuit diagram of an additional embodiment of the electriccircuit contained within the printed wire board on the combinedactuator-accessory module of FIG. 2;

FIG. 6 is a circuit diagram of the components within the circuit of FIG.4; and

FIG. 7 is a circuit diagram of the components within the circuit diagramof FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An integrated circuit breaker 10 consisting of a molded plastic case 11with a molded plastic cover 12 is shown in FIG. 1 with the accessorycover 13 attached to the circuit breaker cover by means of screws 14.The case includes a wiring slot 18 formed therein for allowing externalconnection with a remote switch or alarm. The circuit breaker operatinghandle 19 extends up from an access slot 20 formed in the coverescutcheon 9. A rating plug 15 such as described in U.S. Pat. No.4,728,914 entitled "Rating Plug Enclosure for Molded Case CircuitBreakers" , which Patent Application is incorporated herein forreference purposes is shown assembled within the accessory cover. A pairof accessory doors 16, 17 are formed in the accessory cover forproviding access to the combined electromagnetic actuator and multipleaccessory module 31, hereafter "actuator-accessory module" containedwithin the recess 40, shown in FIG. 2. Still referring to FIG. 2, therating plug 15 is fitted within a recess 23 formed in the accessorycover 13 and the accessory cover is fastened to the circuit breakercover by means of screws 14, thru-holes 24 and threaded openings 25.Access to the rating plug interior for calibration purposes is made bymeans of the rating plug access hole 21.

The trip unit for the integrated circuit breaker 10 is contained withina printed wire board 27 which is positioned in the trip unit recess 26.The rating plug 15 when inserted within the rating plug recessinterconnects with the printed wire board by means of pins 28 upstandingfrom the printed wire board and sockets 29 formed on the bottom of therating plug. An auxiliary switch 22 is positioned within the auxiliaryswitch recess 8 and is similar to that described in aforementioned U.S.patent application Ser. No. 133,868 filed Dec. 16, 1987 entitled "MoldedCase Circuit Breaker Auxiliary Switch Unit". When the auxiliary switchand trip unit printed wire board have been assembled within theirappropriate recesses, the actuator-accessory module 31 is then installedwithin recess 40. The actuator-accessory module includes a housing 32within which the actuator-accessory coil 35 is enclosed and whichfurther contains a plunger 36 and a plunger spring 41 which projects theplunger in a forward trip position against the holding force provided bythe energized actuator-accessory coil 35. The actuator-accessory moduleis similar to the actuator-accessory unit described withinaforementioned U.S. patent application Ser. No. 163,589 wherein a tripactuator latch 37 is pivotally attached to the housing 32. A hook 38formed at one end of the trip actuator latch cooperates with

the circuit breaker operating mechanism shown in aforementioned U.S.Pat. No. 4,700,161 in the manner to be described below in greaterdetail. The operation of the actuator-accessory module is similar tothat described within U.S. Pat. Nos. 4,641,117 and 4,679,019 whichPatents are incorporated herein for purposes of reference. Theactuator-accessory module includes a printed wire board 33 whichcontains the components required for operating the actuator-accessorycoil 35 and is connected with a pair of pins 30 upstanding from the tripunit printed wire board 27 by means of edge connectors 59 which areconnected to the actuator-accessory printed wire board 33. A pair ofwire conductors 34 connect the actuator-accessory module with a voltagesource when undervoltage protection is desired and a separate pair ofwire conductors 60 connect with a voltage source when a shunt tripfunction is desired. The actuator-accessory coil 35 internally connectswith the actuator-accessory printed wire board 33 by means of a separatepair of wire conductors 67, as indicated.

The actuator-accessory module 31 is depicted in FIG. 3 within the recess40 in the integrated circuit breaker 10 with part of theactuator-accessory module printed wire board 33, actuator-accessorymodule housing 32 and accessory cover 13 removed to show the interactionbetween the actuator-accessory module 31 and the mechanical actuator 50which sits in the integrated circuit breaker case 11. The integratedcircuit breaker operating mechanism shown generally at 53 includes anoperating cradle 54 having a hook 55 formed at one end thereof which isretained by means of a primary latch 56. The secondary latch assembly 57prevents the primary latch from releasing the operating cradle until thesecondary latch is displaced. A tab 58 extending from the secondarylatch is contacted by the operation of the mechanical actuator 50 todisplace the secondary latch and thereby articulate the circuit breakeroperating mechanism in response to a trip command in the followingmanner. Electric current flow is sensed by a pair of currenttransformers 47, 48 which are located ahead of load lugs 51, 52. Thecurrent transformers connect with the trip unit printed wire board 27(FIG. 2) by means of conductors 49. The operating lever 46 sits withinthe case 11 and connects with the latch support arm 44 in theactuator-accessory module recess 40 by means of a connecting arm 45. Thelatch pin 43 is retained by the trip actuator latch 37 which is in turncontrolled by the position of the trip actuator arm 39 which extendsthrough a side wall 42 of the actuator-accessory module housing 32. Thetrip actuator arm 39 interfaces with the plunger 36 in the followingmanner. When the circuit current exceeds a predetermined value, theholding current to the actuator-accessory coil 35 is interrupted therebyallowing the plunger 36 to be propelled by the urgence of the plungerspring (FIG. 2) to thereby rotate the trip actuator latch 37 in theclockwise direction to release the trip actuator latch 37 from the latchpin 43.

When undervoltage release function is required along with overcurrentprotection, the circuit depicted at 33A in FIG. 4 is incorporated withinthe actuator-accessory printed wire board 33 shown earlier in FIGS. 2and 3. The actuator-accessory coil 35 is connected with the circuit 33Aby means of terminals T5, T6 and is connected with the remote voltagesource over conductors 34 by means of terminals T₁, T₂. The undervoltagecontrol circuit 61 is similar to that described in aforementioned U.S.patent application Ser. No. 133,869 and provides a holding current tothe actuator-accessory coil 35 until the voltage supplied to terminalsT₁, T₂ drops to a predetermined value, at which time the holding currentis interrupted and the trip function is initiated, as described earlier.The overcurrent trip function is provided by means of the overcurrentcontrol circuit 62 which interacts with the undervoltage control circuit61 by means of the opto-isolator 63 consisting of the light-emittingdiode D₁ and the phototransistor Q₁. The overcurrent control circuitconnects with the trip unit printed wire board 27 of FIG. 2 by means ofterminals T₃, T₄ which comprise edge connectors 59. The edge connectorsconnect with the trip unit printed wire board 27 of FIG. 2 by means ofpins 30, as described earlier.

The operation of the undervoltage control circuit 61 is best seen byreferring now to the detailed circuit 33A' depicted in FIG. 6. Theundervoltage control circuit 61 disables the actuator-accessory coil 35which is connected within the circuit by means of terminals T₅, T₆ thevoltage across terminals T1, T2, falls below a predetermined value for apredetermined time. An external voltage source (not shown) is applied toterminals T1, T2 via conductors 34 (FIG. 4) thereby providing currentthrough the current limiting resistors R₀, R₁ and the rectifierconsisting of diodes D₃ -D₆. One output of the rectifier connects withthe positive bus 70 and the other output of the rectifier connects withthe negative bus 71. A varistor Z₁ is connected across the terminalsthrough resistor R₀ to protect the undervoltage control circuit fromvoltage surges. The actuator-accessory coil 35 is connected between thepositive bus and the drain terminal of an FET₁, the source of the FET₁connects with the negative bus through diode D₈, and resistors R₂, R₉. Afly-back diode D₇ is used to circulate current back through theundervoltage accessory coil when the FET₁ is turned off. Output pin 7 ofa comparator 68 connects with the gate of the FET₁ and input pin 6 ofthe comparator connects with the source of FET₁ through resistor R₃ anddiode D₉. The input pin 6 connects with the negative bus throughcapacitor C₁. The input pin 5 to the comparator connects to the midpointof the test voltage divider consisting of resistors R₆ -R₉ The choppercircuit, consisting essentially of the FET₁ and the comparator, controlsthe current to the actuator-accessory coil 35 in the following manner.With the FET₁ in its "OFF" state, input pin 5 to the comparator is setat 2 volts at the junction of resistors R₇ and R₈. When the voltageacross capacitor C₁ is less than 2 volts, the output pin 7 of thecomparator is "high", turning on the FET₁ and allowing holding currentto flow through the actuator-accessory coil 35. When the FET₁ is on, thecircuit current through diode D₈, develops a proportional voltage acrossR₂ and R₉. Capacitor C₁ charges to this voltage through diode D₉ andresistor R₃. Diode D₈, in series with resistor R₂, provides both voltageand temperature compensation for diode D₉ while resistor R₃ provides ashort time delay during the charging cycle for capacitor C₁ so that thecomparator does not turn off prematurely due to the occurrence of acurrent spike during reverse recovery of diode D₇. For selected valuesof R₂ and R₉ at 30 milliamps circuit current, the voltage developedacross R₂ and R₉ is approximately 3 volts. The voltage across R₉ adds tothe voltage across R₈ to bias input pin 5 of the comparator 68 atapproximately 3 volts. When the circuit current exceeds 30 milliamps,capacitor C₁ will charge greater than 3 volts driving the output pin 7of the comparator to a "low" state, thereby turning off the FET₁. Withthe FET₁ off, the voltage on input pin 5 reverts back to the 2 voltreference value. With 3 volts across capacitor C₁ the output of thecomparator cannot go "high" until the voltage across C₁ drops to lessthan 2 volts. C₁ can only discharge through resistor R₄ which connectsthe output pin 1 of a second comparator 69, which is "low". The value ofresistor R₄ is selected to provide a fixed time delay for the capacitorC₁ to decay to 2 volts thereby establishing a fixed off-time for theFET₁. The circuit current through the undervoltage accessory coil isarranged to turn off at approximately 30 milliamps. Diode D₇ thencirculates the energy stored in the inductance of the actuator-accessorycoil in order to maintain the current at a sufficiently high value toprevent the plunger spring 41, in FIG. 2, from propelling the plunger 36in the forward direction. The circuit current through theactuator-accessory coil decays to approximately 20 milliamps after apredetermined time delay which is determined by the inductive andresistive properties of the actuator-accessory coil. The resistor R₄ isselected to discharge capacitor C₁ 3 volts to 2 volts in the samepredetermined time delay. After the predetermined time delay, the outputpin 7 of comparator 68 goes "high" causing the process just described torepeat itself. If the voltage applied to terminals T1, T2 should at anytime drop below a predetermined value, the output pin 1 of the secondcomparator 69 will go "high" thereby charging the capacitor C₁ up to thepositive rail voltage of the second comparator, which in turn, drivesthe output pin 7 of comparator 68 "low" to turn off the FET₁ . When thevoltage across terminals T₁, T₂, increases, the output pin 1 of thesecond comparator is "low" causing the capacitor C₁ to discharge throughresistor R₄. As soon as the voltage across capacitor C₁ decays to 2volts, FET₁ turns on and the process described earlier is repeated.Resistors R₁₀, R₁₁ connecting across the positive and negative busses70, 71 in combination with the second capacitor C₂, connecting acrossR₁₁, form a simple averaging circuit producing an approximately constantoutput voltage across C₂. The voltage value across C₂ determines thevoltage value above which circuit current is applied to theactuator-accessory coil which value i defined herein as the "pick-up"value and below which, current to the actuator-accessory coil will beinterrupted, which is defined herein as the "drop-out" value. Inoperation, the average voltage established across capacitor C₂ isapplied to the input pin 2 of the second comparator 69 through a currentlimiting resistor R₅. The current limiting resistor R₅ limits thecurrent into the input pin 2 when the voltage across C₂ exceeds thepositive rail voltage applied to the second comparator 69 at pin 8.Input pin 3 of the second comparator is set at approximately 7 volts bythe reference voltage divider R6-R9 which determines the voltageappearing at the connection point between R₆ and R₇. When the

voltage across capacitor C₂ is below 7 volts, the output pin 1 of thesecond comparator 69 goes "high" causing the first comparator 68 tointerrupt the current to the actuator-accessory coil. Conversely, whenthe voltage across C₂ is greater than 7 volts, the output pin 1 of thesecond comparator is "low" thereby permitting comparator 68 to applyturn-on voltage to the gate electrode of the FET₁ which will applycurrent to the actuator-accessory coil. Resistor R₁₂, zener diode D₁₀,transistor Q₃ and capacitor C₃ serve to regulate the voltage at theemitter of Q₃ in the following manner. Resistor R₁₂ and zener diode D₈establish a reference voltage for the base of Q₃ which in turn, suppliesa regulated output voltage to the emitter of Q₃ which is applied to thejunction of pin 8 on the second comparator 69 and to resistor R₆.Resistor R₁₂ and the collector of Q₃ ar connected to one side of astorage capacitor C₄. The undervoltage control circuit 61 requires arelatively low level of steady current, in the order of 1 milliampere,to maintain operation of the discrete electronic devices such as FET₁,comparators 68, 69 and transistor Q₃. A higher level of current, in theorder of 30 milliamps, is applied to the actuator-accessory coil togenerate sufficient magnetic flux to hold the plunger 36 of FIG. 2against the charged plunger spring 41. The 30 milliampere current to theactuator-accessory coil must be maintained while the AC voltage appliedto terminals T1, T2 passes through its zero crossing on each half of theAC cycle. This is accomplished by the combination of FET₂ with resistorR₁₃ and the storage capacitor C₄. Resistor R₁₃, in series with zenerdiode D₁₁, establishes a 33 volt gate reference voltage at the drainelectrode of the FET₂ which sets a charge level of 30 volts for thestorage capacitor C₄. When capacitor C₄ is less than 30 volts and the ACvoltage applied to terminals T1, T2 is greater than 30 volts, the gateelectrode of FET₂ is positive with respect to the source electrode suchthat FET₂ applies charging current to the storage capacitor C₄. As C₄approaches 30 volts, FET₂ turns off to apply the low level steadycurrent requirements described earlier. Accordingly, zener diode D₁₂protects the gate of FET₂ from overvoltage conditions in the event thatthe AC voltage is applied to terminals T1, T2 when the capacitor C₄ iscompletely discharged. With capacitor C₄ fully charged, high ambienttemperatures would otherwise cause leakage current in the FET₂ tofurther charge the capacitor in excess of the rated value of thecapacitor. The zener diode D₁₂ functions to limit the voltage applied tothe storage capacitor C₄ to one diode-voltage above the voltage acrossthe zener diode D₁₁. Zener diode D₁₂ accordingly supplies a negativevoltage to the gate electrode of the FET₂ to reduce the FET₂ leakagecurrent and thereby protect the storage capacitor C₄ from excessvoltage. As described earlier, the storage capacitor C₄ also providesenergy to the actuator-accessory coil when the voltage applied toterminals T1, T2 drops below the 30 volt level. The discharge path forthe storage capacitor C₄ comprises the internal source-drain diode ofFET₂, the actuator-accessory coil, FET₁ , diode D₈ and resistors R₂, R₉.

As described in the aforemetioned U.S. patent application Ser. No.133,869, the undervoltage control circuit 61 is preferred overconventional RC energy storage circuits because of its low powerdissipation at high input voltages which thereby allows the beneficialuse of smaller-sized and lower-rated storage capacitors.

The low power dissipation is provided by the FET₂ in circuit with thestorage capacitor C₄, whereby capacitor C₄ is charged through operationof FET₂ only during the rising part of the wave form of the AC voltageapplied across input terminals T1, T2, typically between 30-80 volts.The FET₂ remains off until the voltage again drops to less than 30volts. Since the peak voltage appearing across the input terminals T1,T2 can exceed 350 volt, charging the storage capacitor C₄ at the lowervoltage level is thus seen to be an important feature for providing thelow power dissipation.

The operation of the overcurrent control circuit 62 within the circuit33A' of FIG. 6 operates in the following manner. When a trip signal isapplied to terminals T3, T4 which terminals comprise the edge connectors59 on the actuator-accessory printed wire board 33 which connects withpins 30 on the trip unit printed wire board 27 as discussed earlier withreference to FIGS. 2 and 4, current flows through the light-emittingdiode D₁ in the opto-isolator 63 and through the current limitingresistor R₁₄. The phototransistor Q₁ in the opto-isolator becomesconductive and thereby transfers current through resistor R₁₇ from theemitter of transistor Q₃ in the undervoltage control circuit 61 which isthe source of the control voltage to the second comparator 69, asdescribed earlier. When Q₁ becomes conductive, current also flowsthrough resistor R₁₆ to the base-emitter junction of transistor Q₄ whichturns on Q₄ thereby discharging capacitor C₂ within the undervoltagecontrol circuit which connects with Q₄ by means of conductor 64. Thedischarge of C₂, which provides the test voltage to the secondcomparator 69, simulates an undervoltage condition thereby interruptingthe holding current supplied to the actuator-accessory coil 35 in themanner described earlier. The parallel combination of resistor R₁₅ andcapacitor C₅ connected across the emitter and base of thephototransistor Q₁ prevent the phototransistor from falsely becomingconductive by electrical environmental noise.

Undervoltage release function, overcurrent protection and shunt tripfacility is provided by means of circuit 33B depicted in FIG. 5 whichcircuit is incorporated within the actuator-accessory printed wire board33 of FIGS. 2 and 3. The undervoltage control circuit 61 operates tointerrupt circuit current by interrupting the holding current to theactuator-accesory coil 35 in the manner described earlier with referenceto FIGS. 4 and 6. The overcurrent control circuit 62 also interacts withthe undervoltage control circuit by means of opto-isolator 63 in themanner described earlier. The shunt trip control circuit 72 connectswith external wire conductors 60 by means of terminals T7, T8 andinteracts with the undervoltage control circuit 61 by means ofopto-isolator 66. To institute a shunt trip operation, thelight-emitting diode D₂ is energized, which turns on the phototransistorQ₂, in the same manner described earlier for the light-emitting diode D₁and phototransistor Q₁ within the opto-isolator 63.

The use of a combined undervoltage release, overcurrent and shunt tripcircuit was heretofore impractical because of the electric isolationproblems involved with the individual circuits. For example, the voltagesignal applied to perform a shunt trip function could evolve from adifferent source from that of the undervoltage control circuit therebyrequiring electrical isolation between the two circuits. The use ofopto-isolators between the shunt trip and undervoltage circuits providessuch electrical isolation without undue cost and complex circuitry. Thisis also true for the overcurrent control circuit which is generally fedfrom a voltage source other than the one used with the undervoltage andshunt trip control circuits.

The operation of the overcurrent, undervoltage and shunt trip circuitsof FIG. 33B can best be seen by referring now to the detailed circuit33B' depicted in FIG. 7. The undervoltage control circuit 61 and over

current control circuit 62 .operate in the same manner as describedearlier with reference to FIGS. 4 and 6. The operation of the shunt tripcontrol circuit 72 is seen as follows. A trip signal is applied overexternal wire conductors 60 (FIG. 5) to terminals T7, T8 which connectthrough current limiting resistor R₁₈ and diode pairs D₁₂, D₁₃ to astorage capacitor C₆. Transistors Q₆, Q₇, silicon switch Q₈ andresistors R₁₉ and R₂₀ are connected together to form an electronicswitch 74. The voltage developed across capacitor C₆ is applied to oneside of the electronic switch through a current limiting resistor R₂₁and to the other side thereof through the light-emitting diode D₂ of theopto-isolator 66. When the voltage across the silicon switch Q₈ exceedsits rated break-over voltage, it becomes conductive thereby drawingcurrent through resistor R₂₀ and the emitter-base junction of transistorQ₇ causing Q₇ to become conductive. With Q₇ conducting, current isapplied to the base-emitter junction of transistor Q₆ and resistor R₁₉such that Q₆ also becomes conductive. With Q₆ conductive, silicon switchQ₈ turns off and Q₆ forces more current to flow through transistor Q₇causing light-emitting diode D₂ to turn on. The phototransistor Q₂ thenbecomes conductive causing current to flow through the undervoltagecontrol circuit 61 by means of conductor 65 and current limitingresistor R₂₂ to the base-emitter junction of transistor Q₅. Q₅ turns onand discharges capacitor C₂ which now appears to the input of comparator69 as an undervoltage condition thereby turning off the holding currentto the actuator-accessory coil 35 in the manner described earlier.Control power is returned to tee `35 overcurrent control circuit 62 bymeans of conductor 73 which connects with the negative bus 71 a one endand to the base of the transistor Q₄ through current limiting resistorR₁₆ at an opposite end. Control power is returned to the shunt tripcontrol circuit 72 by means of conductor 73 and current limitingresistor R₂₃ which connects with the base of transistor Q₅. Capacitor C₇and resistor R₂₄ connect across the base and emitter of phototransistorQ₂ to prevent the phototransistor from becoming falsely renderedconductor by electrical environment noise. The overcurrent controlcircuit 62 which connects with the undervoltage control circuit throughtransistor Q₄ and conductor 64 operates in the same manner tode-energize the actuator-accessory coil 35, as described earlier withreference to FIG. 6.

The arrangement of the components within the above described electronicswitch 74 is an important feature of the invention. Specifically, theelectronic switch minimizes heating effects caused by current flowthrough the shunt trip control circuit. The value of the cur- rentlimiting resistor R₁₈ is selected to allow rapid charging of the storagecapacitor C₆ while at the same time providing a holding current for theelectronic switch which is above the charging current provided to thestorage capacitor. This insures that the electronic switch does notremain in a latched-on condition after the storage capacitor hasdischarged.

Heretofore, when a circuit breaker was installed with a shunt tripdevice to articulate the circuit breaker operating mechanism andseparate the circuit breaker contacts, some additional means was alsorequired to turn off the remote shunt trip current in order to protectthe electromagnetic coil used within the shunt trip device. An auxiliaryswitch such as described in aforementioned U.S. patent application Ser.No. 133,867 mechanically interacted with the circuit breaker operatingmechanism to interrupt the shunt trip current flow to the shunt tripelectromagnetic coil. The shunt trip control circuit 72 shown in FIG. 7automatically controls the shunt trip control current by operation ofthe electronic switch thereby permitting continuous energization of theshunt trip accessory function without requiring an auxiliary switch.

A modular actuator-accessory arrangement has herein been described whichallows selected accessory function to be either field-installed orfactory-installed by means of selected actuator-accessory modules. Theactuator-accessory module completely contains the mechanical componentsrequired to interface with the associated circuit breaker mechanism toarticulate the circuit breaker operating mechanism along with theelectronic logic required for each selected protection facility within asingle module entity.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:
 1. A circuit breaker actuator-accessorymodule circuit comprising:an undervoltage release electromagnetic coil;a spring-biased plunger associated with said coil; an undervoltagecontrol circuit connected with said coil, said undervoltage circuitincluding means for interrupting holding current to said coil andallowing said plunger to propel into contact with a trip lever uponreceipt of a predetermined undervoltage signal to said undervoltagecircuit; and an overcurrent control circuit interacting with saidundervoltage circuit through an opto-isolator said overcurrent circuitincluding means for interrupting said holding current upon receipt of apredetermined overcurrent signal to said overcurrent circuit.
 2. Theactuator-accessory module circuit of claim 1 wherein said opto-isolatorincludes a phototransistor connected with said undervoltage circuitthrough a first transistor switch and a light-emitting diode connectedwith a first pair of input terminals to said overcurrent circuit forreceiving said overcurrent signal.
 3. The actuator-accessory modulecircuit of claim 2 wherein said undervoltage circuit means includes afirst comparator connected with said electromagnetic coil through afirst FET.
 4. The actuator-accessory module circuit of claim 3 includinga second FET connected with said first comparator through a secondcomparator and a second transistor switch.
 5. The actuator-accessorymodule circuit of claim 4 wherein the base and emitter on said firsttransistor switch connects with the emitter on said phototransistor. 6.The actuator-accessory module circuit of claim 5 wherein the collectoron said first transistor switch connects with test voltage means whichconnect with a first input to said second comparator.
 7. Theactuator-accessory module circuit of claim 6 wherein said undervoltagecircuit means includes a second pair of input terminals connecting witha diode bridge rectifier for receiving said undervoltage signal, a firstoutput from said rectifier connecting with one side of saidelectromagnetic coil, a second output from said rectifier connectingwith said emitter on said first transistor switch.
 8. Theactuator-accessory module circuit of claim 7 including a zener diodeconnected between the source terminal and the gate terminal of saidsecond FET.
 9. The actuator-accessory module circuit of claim 8 whereinthe source terminal on said first FET connects with a first input tosaid first comparator and with an output from said second comparator,the drain terminal on said first FET connects with the other side ofsaid electromagnetic coil.
 10. The actuator-accessory module circuit ofclaim 6 wherein said test voltage means comprises a first voltagedivider.
 11. The actuator-accessory module circuit of claim 10 whereinsaid first voltage divider comprises a first pair of resistors connectedbetween a negative voltage supply bus and a positive voltage supply bus.12. The actuator-accessory module circuit of claim 10 wherein a secondinput to said first comparator and a second input to said secondcomparator connect with reference voltage means.
 13. Theactuator-accessory module circuit of claim 12 wherein said referencevoltage means comprises a second voltage divider.
 14. Theactuator-accessory module circuit of claim 13 wherein said secondvoltage divider comprises a second and third pair of resistorsconnecting between the emitter of the second transistor switch and thenegative voltage supply bus.
 15. The actuator-accessory module circuitof claim 14 wherein said second pair of resistors connect with thesecond input to said first comparator.
 16. The actuator accessory modulecircuit of claim 14 wherein said third pair of resistors connect withsaid second input to said second comparator.
 17. A circuit breakeractuator-accessory module circuit comprising:an undervoltage releaseelectromagnetic coil; a spring-biased plunger associated with said coil;an undervoltage control circuit connected with said coil, saidundervoltage circuit including means for interrupting holding current tosaid coil and allowing said plunger to propel into contact with a triplever upon receipt of a predetermined undervoltage signal to saidundervoltage circuit; an overcurrent control circuit interacting withsaid undervoltage circuit through a first opto-isolator, saidovercurrent circuit including means to interrupt said holding currentupon receipt of a predetermined overcurrent signal; and a shunt tripcontrol circuit interacting with said undervoltage circuit through asecond opto-isolator, said shunt trip circuit including means tointerrupt said holding current upon receipt of an external commandsignal.
 18. The circuit breaker actuator-accessory module circuit ofclaim 17 wherein said first opto-isolator includes a firstphototransistor connected with said undervoltage circuit through a firsttransistor switch and a first light-emitting diode connected with afirst pair of input terminals to said overcurrent circuit for receivingsaid overcurrent signal.
 19. The circuit breaker actuator-accessorymodule circuit of claim 18 wherein said second opto-isolator includes asecond phototransistor connected with said undervoltage circuit througha second transistor switch and a second light-emitting diode connectedwith said shunt trip circuit.
 20. The circuit breaker actuator-accessorymodule circuit of claim 19 wherein said undervoltage circuit meansincludes a first comparator connected with said electromagnetic coilthrough a first FET.
 21. The circuit breaker actuator-accessory modulecircuit of claim 20 including a second FET connected with said firstcomparator through a second comparator and a third transistor switch.22. The circuit breaker actuator-accessory module circuit of claim 21wherein the base and emitter on said first transistor switch connectswith the emitter on said first phototransistor.
 23. The circuit breakeractuator-accessory module circuit of claim 22 wherein the collector onsaid first transistor switch connects with test voltage means whichconnect with an input to said second comparator.
 24. The circuit breakeractuator-accessory module circuit of claim 23 wherein said undervoltagecircuit means includes a second pair of input terminals connecting witha diode rectifier for receiving said undervoltage signal, a first outputfrom said rectifier connecting with one side of said electromagneticcoil, a second output from said rectifier connecting with said emitteron said first transistor switch.
 25. The circuit breakeractuator-accessory module circuit of claim 24 including zener diodeconnected between the source terminal and the gate terminal of saidsecond FET.
 26. The circuit breaker actuator-accessory module circuit ofclaim 25 wherein the source terminal on said first FET connects with afirst input to said first comparator and with an output from said secondcomparator, the drain terminal on said first FET connects with the otherside of said electromagnetic coil.
 27. The circuit breakeractuator-accessory module circuit of claim 26 wherein said overcurrentmeans includes a second pair of terminals connected with said firstlight-emitting diode for receiving said overcurrent signal.
 28. Thecircuit breaker actuator-accessory module circuit of claim 27 whereinsaid shunt trip circuit means includes a third pair of terminals forreceiving said external command signal.
 29. The circuit breakeractuator-accessory module circuit of claim 28 including a storagecapacitor connecting with said third pair of terminals through a secondsignal bridge diode rectifier.
 30. The circuit breakeractuator-accessory module circuit of claim 29 including an electronicswitch connecting between said storage capacitor and said secondlight-emitting diode for regulating said external command signal. 31.The circuit breaker actuator-accessory module circuit of claim 30wherein said electronic switch includes a fourth transistor switchconnected in series with said second light-emitting diode through afirst resistor.
 32. The circuit breaker actuator-accessory modulecircuit of claim 31 including a fifth transistor switch within saidelectronic switch, said fourth transistor switch being connected inseries with said second light-emitting diode.
 33. The circuit breakeractuator-accessory module circuit of claim 32 including a silicon switchconnecting between the base of said fourth transistor switch and theemitter of said fifth transistor switch.
 34. The circuit breakeractuator-accessory module circuit of claim 33 wherein said test voltagemeans comprises a first voltage divider.
 35. The circuit breakeractuator-accessory module circuit of claim 34 wherein said first voltagedivider comprises a first pair of resistors connected between a negativevoltage supply bus and a positive voltage supply bus.
 36. The circuitbreaker actuator-accessory module circuit of claim 35 wherein a secondinput to said first comparator and a second input to said secondcomparator connect with reference voltage means.
 37. The circuit breakeractuator-accessory module circuit of claim 36 wherein said referencevoltage means comprises a second voltage divider.
 38. The circuitbreaker actuator-accessory module circuit of claim 37 wherein saidsecond voltage divider comprises a second and third pair of resistorsconnecting between the emitter of the second transistor switch and thenegative voltage supply bus.
 39. The circuit breaker actuator-accessorymodule circuit of claim 38 wherein said second pair of resistors connectwith the second input to said first comparator.
 40. The circuit breakeractuator-accessory module circuit of claim 39 wherein said third pair ofresistors connect with said second input to said second comparator.